1. Field of the Invention
The subject invention relates to the method of controlling a powered manipulator within a plurality of distinct workspaces. More specifically, the subject invention relates to establishing and repositioning at least one virtual constraint from a first workspace to a second workspace such that movement of the powered manipulator in the second workspace is limited to prevent the operator from moving the powered manipulator to at least one physical limit of the second workspace.
2. Description of the Prior Art
The moving of heavy objects from one location to another traditionally is accomplished by the use of a powered manipulator or more typically, an unpowered manipulator that utilizes overhead rails or a bridge gantry with a carriage movably supported thereon. An arm is pivotally attached to the carriage to lift the objects from overhead. When moving a heavy object, it is desirable to have the operator as close to the object as possible to make movement of the object more intuitive as if the operator was actually lifting and moving the object. To this end, it is desirable to utilize power assisted manual manipulators.
Methods to control a power assisted manual manipulator must provide adequate operator safety and still provide an intuitive human interface. One method of controlling an assist device is comprises the steps of utilizing an actuator to sense the required force for lifting a load, providing an end-effector to interface between a human operator and the load, engaging the load with the end effector, detecting a magnitude of human force imparted by the operator on the end-effector as the operator lifts the load and using the magnitude of the human force to regulate the actuator and cause the actuator to lift the load. This method utilizes the imparted force by the operator to govern the force provided to assist in lifting the load. In this way an operator maintains the feel of lifting the load and moving it but exerts only enough force to control the moving of the load.
Another method of moving a load is exemplified by a power assist device used by an operator to pick up an instrument panel off a rack and guide the instrument panel into a vehicle cabin for attachment therein. The operator does not support the weight of the instrument panel and is free to move the instrument panel around the workspace without constraint. The deficiency in this method is that there is no restraint on powered manipulator motion. As a result, the power assist device can be freely wielded by the operator, and the operator may inadvertently move the instrument panel into anything, damaging both the instrument panel and whatever the panel hits.
The above methods are further deficient in that they are unable to adjust easily to compensate for parts with particular features that vary from part-to-part, or they are unable to adjust easily to compensate for parts that are disposed on a support rack in varying positions each time. Also, these methods are unable to track an assembly line as the assembly line is operating or these methods rely on the operator to apply the equivalent force required to match a speed of the assembly line.